Character generation logic



March 11, 1969 c. R. WINSTON 3,432,844

CHARACTER GENERATION LOGIC Filed April 21. 1965 Sheet of 8 FIG. I

a-GATE 2 T CHARACTER ooT 23 DEFLECTION CHARACTER CORE DECODER MATRIX ARRAY CIRCUITS CODE DOT INPUT MATRIX 22 r f COLUMN a GATE SELECTOR FUNCTION DECODER INH CLOCK l3 CHARACTER TIMING INPUT Fl IG.

INVENTOR FIG 7 CHARLES R. WINSTON FIG. FIG. FIG.

ATTORNEY.

March 11, 1969 c. R. WINSTON 3,432,344

CHARACTER GENERATION LOGIC Filed April 21, 1965 Sheet 2 March 11, 1969 c. R. WINSTON CHARACTER GENERATION LOGIC Sheet Filed April 21, 1965 LINE FEED MECH.

BELL MECH.

March 11, 1969 c. R. WINSTON 3,432,844

CHARACTER GENERATION LOGIC Filed April 21, 1965 Sheet 5' of 8 FIG. 5

; March 1969 c. R. WINSTON 3,432,844

CHARACTER GENERATION LOGIC Filed April 21, 1965 Sheet 6 of8 March. 11,1969 c. R. WINSTON 3,432,844

CHARACTER GENERATION LOGIC Filed April 21, ,1965 v Sheet 7 of 8 FIG. 8

OUTPUT OUTPUT FIG. IO

FIG. 9

C. R. WINSTON CHARACTER GENERATION LOGIC March 11, 1969 Sheet Filed April 21, 1965 FIG.

United States Patent 8 Claims ABSTRACT OF THE DISCLOSURE An electrostatic printer employs 40 printing nozzles located across a page width to print 80 character lines with each nozzle printing two characters and with printing taking place sequentially a character at a time. At all times, three adjacent nozzles are turned on with the outer two of the three having the ink streams being deflected onto a mask and with printing taking place only from the center one of the three nozzles. Permutationcoded input characters are decoded in two groups of AND-gates, the outputs of which are supplied to a diode matrix to provide a single digital output for each different input character. Each output of the diode matrix is variably threaded through selected ones of the cores of a fixed wired ferrite core memory, with each core individually associated with a different dot location in the matrix out of which the character is to be formed; and only those cores associated with the selected character are set. The set cores then are sequentially interrogated one at a time under control of a dot diode matrix having a diode crosspoint for each dot location in the character matrix. Interrogation is accomplished by resetting a set core, causing signals to be supplied on permutation-coded output windings to a storage register, the output of which is used to supply control signals to the deflection electrodes associated with the printing nozzles. The output of the register also is supplied to the diode matrix to select (in conjunction with a clock pulse) the diode for the next dot location to be interrogated and the sequence is repeated. When the last memory core for a given character is reset, the interrogation is stopped and the system is reset awaiting receipt of the next input permutationcoded character.

SPECIFICATION This invention relates to character synthesis and more particularly to the synthesis of dot-matrix-formed characters by sequentially generating two-dimensional representations of the locations of the various dots going to make up each character.

Much ingenuity and considerable research have resulted in the development of mechanical and electromechanical printing devices to a relatively high degree of refinement with respect to printing speed, efliciency and reliability. The operating speed of these devices, however, is always limited by the inherent mechanical inertia of the component moving parts and by available power. The highest speeds for mechanical and electromechanical printers have been achieved by parallel operation, i.e., in such manner that an entire line of characters is printed simultaneously. Such operation, however, always entails storage of the entire line of information to be printed, resulting in additional equipment and increased complexity being introduced into the system. Serial operation, while not requiring such storage and not subject to the resultant limitations imposed thereby, dictates a far lower maximum printing speed. Thus, the need for a printing means capable of greater speed than the fastest mechanical system, but with serial operation, is manifest. Such a device may be employed, for example, for recording output data from an electronic computer, for accepting and recording information from a magnetic tape or drum or other type storage medium, or for recordingtelegraphic transmission as it is received one character at a time over a high-speed telegraph line.

Electronic methods of character synthesis are practically free of inertia and therefore inherently capable of serial type operation at very high speed. The present invention is therefore directed toward an improved apparatus and method whereby character synthesis may be accomplished in a serial type operation by means of a beam of marking material that is deflected from place to place within a printing field under control of the character synthesis system in order to trace or draw the desired character on the paper or other marking medium. Thus, in beam-type printing, a beam is used to control the deposit of ink on paper and becomes the pen with which the character is formed. This beam may be light, electrons in a vacuum tube, or a stream of charged ink droplets as disclosed in the patent to C. R. Winston, No. 3,060,429, granted Oct. 23, 1962.

Synthesis of the character to be printed is usually on a dot-matrix pattern with the beam or marking source forming the character by moving from dot-location to dot-location tracing out the desired character. To control the tracing of the character, two-dimensional representations of the locations of the various dots which make up a character must be generated serially in the proper sequence.

It is an object of the present invention to synthesize a character for display by generating a sequence of twodimensional deflection signals.

Another object of the present invention is to control the generation of printed characters by converting coded input signal into a succession of pairs of deflection signals in a predetermined time sequence, each of the signals of a pair of deflection signals constituting the location or address which defines the coordinates of a dot in the character represented by the coded input signal.

Still another object of the invention is to control the deflection of a beam of ink droplets to print characters on a recording medium.

A further object of the invention is to control the defiection of an electrostatically generated stream of ink droplets in order to locate each droplet in a selected sequence to form a character.

A still further object of the invention is to print page copy at high speed by providing a plurality of marking sources across a page and controlling their sequential operation.

Yet another object of the invention is to selectively energize one or more marking sources of a plurality of marking ray sources available.

In accordance with the preferred embodiment of the invention for controlling the deflection signals applied to the deflection electrodes of a printing device of the type disclosed in the aforementioned patent to C. R. Winston and for use in a high-speed telegraph page printer, a digital representation in a permutation code of the character to be printed is first applied simultaneously to a plurality of code input terminals. This code is monitored by a multiplicity of AND-gates. Certain of these AND-gates are used to decode and recognize nonprinting or function permutations, and the rest of these AND-gates begin the decoding process for the printed char-acters. At approximately the chronological center of the simultaneous pulses which carry the permutation code signal, a character-timing signal is received which triggers the completion of the decoding of the character then being received. Character recognition occurs by setting a plurality of ferrite switch cores. These switch cores are then reset one at a time. Each core is selectively wired with output windings; and as each core is reset, it generates a pulse over each of the output windings that have been threaded through it. This output is the digital representation in two dimensions of the location of one of the dots going to make up the character decoded. This digital representation of the dot location is then used to determine which of the previously set cores is to be reset next. The last core to be reset signals the end of a character cycle and prepares the system for receipt of the next character.

To print a page width of visible copy, it is necessary that many of the printing devices shown in the aforementioned patent to C. R. Winston be used side by side. A column selector is used to determine which one or ones of the individual printing devices are operating at any given time. The signal which indicates the end of a printing cycle also causes the column selector to effect spacing of the printer by advancing operation of the printing devices such that the next character is printed in the next column to the right of the character just printed.

A more complete understanding of the invention may be had from the following description considered together with the accompanying drawings wherein:

FIG. 1 is a simplified logic block diagram of the character synthesis system;

FIGS. 2 to 6, inclusive, when arranged together in the manner illustrated in FIG. 7, form a detailed logic diagram of the character synthesis system shown in the block diagram of FIG. 1;

FIG. 8 shows the input read-out and output arrangement of a typical ferrite core-type memory element used in the system;

FIG. 9 is a diagram of the dot-matrix printing with the character B superimposed thereon;

FIG. 10 is a schematic diagram of the bistable multivibrator used in the synthesis system, showing the gating arrangement of the inputs to the multivibrator, and

FIG. 11 shows the digital-to-analog converters operating the deflection electrodes of the ink transferring device of the Winston patent.

GENERAL DESCRIPTION In the preferred embodiment of the invention as illustrated in FIG. 1, a character in the form of permutationcode electronic signals appearing simultaneously over a plurality of wires is applied to a code input 10. These simultaneous signals are carried to an AND-gate function decoder 11 and an AND-gate character decoder 12. In the format of a telegraph code, most of the signal permutations represent characters or figures to be printed; however, certain of the signal permutations represent nonprinting functions to be performed by the printer, such as spacing without printing (as is provided by the spacer bar on the typewriter), the ringing of a bell to signal an operator, carriage return to cause the subsequent character to be printed at the left margin of the page, and line feed to move the page copy in order to begin printing on the next line. As soon as the character permutation signals are presented in the code input 10, the function decoder 11 begins recognition to determine whether or not that permutation code combination represents a nonprinting function. If the code combination is a nonprinting function, operation of the major portion of the character synthesis system is inhibited. At approximately the midpoint of the period of presentation of the pulses comprising the permutation code combination at the code input 10, a character timing signal is received over character timing input 13. This character timing signal indicates the optimum moment for recognizing the permutation code combination then being presented at code input 10 and also provides a time base to which the remainder of the functions of the printer can be referred. If the permutation code combination being presented at code input 10 is a nonprinting function, such as a line feed signal, the character timing signal is inhibited, by inhibitor 17, from energizing anything other than the function decoder; but the character timing signal initiates operation of the function. If the code combination presented at input 10 represents a character to be printed, decoding of this character begins immediately upon presentation of the coded signal to the AND-gate character decoder 12. Outputs 14 from the AND-gates 12 represent only a partially decoded character. These outputs 14 are combined in a character matrix 15 which, upon receipt of the character timing signal, uninhibited by recognition of a nonprinting function, completes the decoding of the character by setting a selected combination of switch cores contained in a dot core array 16, to their one state. This selected combination of switch cores represents that character being presented in permutation code for-m at code input 10, with each individual switch core representing one of the many dots which form the actual shape of the character on a dotformed-matrix type font.

The same character-timing signal which completes the decoding of the permutation code character also initiates operation of a local clock 20. This local clock 20 determines the rate at which dots are printed. As each core of the received character is reset to its zero state, the output of that core is presented over wires 23 to the deflection circuits 24 of the printer. This output is in the form of a digital representation in two dimensions of the location of the dot, associated with that core, in the dot matrix pattern of the character which is being printed. The deflection circuits 24 comprise digital-to-analog converters which change the digital signals to discrete voltage levels which are applied to the deflection electrodes of the ink transferring device disclosed in the Winston patent referred to hereinbefore.

This digital representation of the location of the dot is also sent to a dot-matrix 21 that determines which of the cores will be reset next. When the last core of the particular character being printed is reset, a signal is sent to the clock 20 to turn off the clock in order to prepare the printer for receipt of the next character. This same signal is also sent to the column selector 22 in order to cause the next character to be printed in the next space to the right.

In the patent to C. R. Winston mentioned above, disclosing apparatus for transferring ink, the device is shown printing characters on a strip of tape that is moved across the printing field of the device in order to permit each character to be printed in the same location with respect to the nozzle from which ink issues. If, however, it is desired to print material by this technique on a pagewidth of paper such as is done on a standard ofiice typewriter, some provision must be made to either move the paper past the printing nozzle or to move the ink transfer device across the width of the paper. In page printing machines intended for unattended remote operation, it is common practice to move the page-width paper only longitudinally; that is, to move the paper in a vertical direction with respect to an operator reading the printed copy. The typing means is moved horizontally, while the paper is not; therefore, provision must be made for printing across a full 70-to-80-character line without moving the paper.

It has further been found that the ink transferring device considered herein can successfully print two adjacent characters without introducing excessive distortion of the character shape. In order to print two characters with a single nozzle, a large horizontal deflection is first imparted to the stream of ink droplets in order to locate the point of impingement of the stream of ink droplets onto the paper substantially to the left of the center line of the nozzle. A character is then printed which is totally to the left of the center line of the nozzle. After this character has been printed, a substantial rightward deflection is imparted to the stream of ink droplets deflecting the stream of ink droplets to the right of the center line of the nozzle and printing a complete character wholly to the right of the nozzle center line. During idle periods of the stream of ink droplets, at which time it is not printing characters on the paper, a large vertical deflection is imparted to the stream deflecting it downwardly onto a mask which is provided in front of the paper and below the printing field. Since a single nozzle can effectively print two adjacent characters, an apparatus has been constructed using forty of the ink transferring devices of the Winston patent, spaced evenly across a page of a telegraph printer with such spacing between the nozzles that there is one nozzle for each two characters to be printed across the page of paper. Control must be provided for determining whether or not any given nozzle is printing to the left or right of its center line and the streams must also be controlled so as to determine which nozzle or nozzles are printing at any given time.

In controlling the sweep of a cathode-ray tube, the cathode-ray tube can be turned on and off by the grid of the cathode-ray tube without significant worry over the effect of turn-on and turn-off transients; that is, irregularity of the display due to the fact that the cathode-ray is being turned on or turned off. It has been found that in the operation of the ink transfer device disclosed in the Winston patent significantly erratic operation of the stream of ink droplets was noted during the period in which flow of the stream of ink droplets was developing, such that unacceptable printing was experienced. For this reason, a stream of ink droplets is first deflected downwardly onto the mask in front of the paper until the stream develops a steady-state flow pattern. At this point, once the ink flow pattern is fully developed, the stream is raised upwardly into the printing field and made to trace the character while maintaining a full rate of flow during the entire printing cycle. The stream can then be lowered onto the mask and turned off.

In printing at high speeds, the time required to develop a full flow of ink is sometimes sufficiently long that it is advantageous to turn on a stream long before it is to print a character and thus warm up the stream. It is undesirable to have all of the streams turned on at all times since this wastes ink. Therefore, all the nozzles are turned off except when printing, and as printing is accomplished across the width of a page, each nozzle prints its two characters while the nozzle to its right is warming up and developing its pattern of flow. Therefore, at least two streams are flowing at any given time. Since the voltages involved in extracting a stream of ink droplets from a nozzle under negligible hydrostatic pressure are relatively large, a significant electrostatic field exists around each stream of ink droplets. In order to minimize the distortion of the character being printed by a given nozzle due to the effect of the electrostatic field generated by the nozzle to the right which is in the process of warming up, the preceding nozzle to the left of the printing nozzle is also permitted to remain in operation in order to provide a comparable electrostatic field to the left of the printing nozzle. Thus, it is desirable to maintain a flow of ink droplets from three adjacent nozzles simultaneously while at all times deflecting the streams from the outer two of these three nozzles onto the mask.

Function decoder FIGS. 2, 3, 4, 5, and 6 when arranged according to FIG. 7 show a more detailed logic diagram of the character generator of FIG. 1. In FIG. 3 a six-unit or sixlevel permutation code signal is presented to the six inputs of code input 10. Each level of the code signal is inverted by one of the inverters 30 in order to produce a signal which is of the opposite binary sense or polarity of the associated code signal. This produces a permutation code signal on six pairs of Wires 35 with one wire of the pair carrying the bit which has been fed into the code input 10 and the other wire of the pair carrying a signal of opposite binary polarity. These six pairs of code signals existing on wires 35 are sent to the AND- gate function decoder 11 and the AND-gate character decoder 12a and 12b. The AND-gate function decoder 11 consists of four, five-input AND-gates. The AND- gates 40, 50, 55, and 58 of function decoder 11 are each selectively wired to five of the twelve wires 35 in order for each gate to recognize only one of the 64 possible permutations of the six-level code presented at code input 10. If a permutation code combination signal is received at code input 10, which represents spacing, in order to initiate a spacing function similar to that of the spacing bar on a typewriter, that code combination will energize AND-gate 40 of the function decoder 11 producing an output signal on spacing output wire 41. The signal on spacing output wire 41 performs two operations. This signal primes a spacing gated amplifier 42 and energizes a print-suppression OR-gate 45. The output of print suppression OR-gate 45 appears on print suppress-wire 46 and energizes inhibit gate 17 to pre vent the recognition and printing of any printing character.

The pulses of the permutation code signal sent to code input 10 are of finite chronological duration. At the chronological center of these pulses, a character timing pulse is received at a character timing input 13. This character timing pulse is carried over character timing wire 47 to inhibit gate 17 and spacing gated amplifier 42. This character timing signal cannot pass through inhibit gate 17 due to the print suppression signal appearing on print suppress wire 46. However, the character timing signal on character timing wire 47 does trigger spacing gated amplifier 42 in order to permit the spacing signal on spacing output wire 41 to pass through spacing gated amplifier 42 in order to cause the printer to space. The spacing function of the printer is similar to the spacing function in a typewriter with the exception that instead of spacing in response to actuation of the spacing bar of the typewriter, the printer spaces in response to receipt of a spacing signal as recognized by spacing AND-gate 40.

In the event that the code combination received the code input 10 is a carriage-return signal, carriage-return AND-gate 50 will be energized. The output of carriagereturn AND-gate 50 also performs two operations. This output energizes print suppression OR-gate 45 and primes carriage-return gated amplifier 51 which, like spacing gated amplifier 42, is triggered by a character timing signal appearing on character timing wire 47, causing a carriage return signal to appear on carriage return wire 52. When a signal appears on carriage return wire 52, it causes the next printed character received to be printed at the left-hand margin of the page much the same as on a typewriter. The spacing and carriage-return functions will be described more fully in conjunction with the column selector shown in FIG. 6.

In the event that the character received at character input 10 is a line-feed character, line-feed AND-gate 55 will be energized. The output of the line-feed AND-gate 55 operates the print-suppress OR-gate 45 and also energizes line-feed gated amplifier 56. Upon receipt of the character-timing signal over character-timing wire 47, this line feed signal is sent to the line feed mechanism 57 which causes the paper in the printer to advance, in order to print the succeeding character on the next line of the page copy. If the character received is a bell character, it will energize bell AND-gate 58 which functions the same as line-feed AND-gate 55 with the exception that it energizes bell-ringing mechanism 59 instead of line-feed mechanism 57.

AND-gate character decoder At the same time that the AND-gate function decoder 11 is attempting to determine whether or not the input character at code input 10 is a nonprinting function, the AND-gate character decoder 12 is attempting to decode this character as it appears on wires 35. These six pairs of wires making up wires 35 are broken down into two groups of three pairs each. One group of three pairs of wires is used to energize one group 12a of eight threeinput AND-gates and the other group of three pairs of wires is used to energize another group 12b of eight three-input AND-gates. In a. permutation code, three binary bits give rise to eight possible, distinct permuta tions; therefore, each group of three pairs of wires energizes a selected one of its associated group of eight AND- gates in response to any given permutation code combination. Since AND-gate character decoder 12 consists of two groups of eight AND-gates, one of the eight AND- gates of one of the groups when combined with one of the AND-gates of the other group, defines one of 64 possible combinations. The sixteen outputs from the AND- gate character decoder 12 are shown in FIG. 1 as outputs 14 and are shown providing the inputs to character matrix 15. The outputs 14a from the AND-gates 12a are used to prime gated amplifiers 65 while the outputs 1411 from AND-gates 12b provide the inputs for gated amplifiers 66. In the event that a non-printing function code combination is received at code input 10, print suppression wire 46 will carry a print-suppression signal and inhibit gate 17 will be energized. However, if a printing code combination is received at code input 10, there will be no print-suppression signal on wire 46, and the character timing pulse carried on wire 47 will pass through inhibit gate 17. The output of inhibit gate 17 performs two operations. This output starts the local clock 20 which will be discussed in more detail below and is also sent over matrix trigger wire 67 to trigger the gated amplifier 65 that has been primed. Since only one of the gated amplifiers 65 has been primed by its associated AND-gate of AND-gates 12a only one of the matrix wires 68 will be energized. Similarly, since only one of the AND-gates 1212 has been selected, only one of the orthogonal matrix wires 69 will be energized. A plurality of character diodes join the matrix wires 68 and orthogonal matrix wires 69. That diode which joins the energized one of the matrix wires 68 with the energized one of the orthogonal matrix wires 69 will conduct a pulse of current when matrix trigger wire 67 triggers gated amplifiers 65. This pulse of current completes the decoding of the code combination received at code input 10.

Dot core arrangement The dot core array 16 used in the synthesis of the characters to be printed contains a plurality of ferrite cores, each corresponding to a different directed line segment or vector of the trace pattern which can be developed by use of the dot core array 16.

In order more fully to understand the description of the operation of the dot core array, it should be noted that each core represents a different vector or line segment extending from a given dot location or dot position to another dot location in the dot matrix out of which the characters are to be formed. This does not mean that there is only a single core for each dot position, but rather it is possible to have several cores for each dot position, each core representing a different vector which extends from that dot position to another. Thus, the core matrix 16 includes a greater number of cores than the number of possible dot locations in thecharacter matrix, and the selection of the desired core for each of these different dot positions depends upon the particular character or symbol to be synthesized. The means by which the pulse of current passing through the selected diode of the core matrix completes the decoding of the character is best explained in conjunction with FIG. 8 wherein there are shown, by way of example, three toroidal ferrite cores 75, 76 and 77 out the total number of cores in the dot core array. A plurality of character wires 78 pass through selected ones of the cores (including 75, 76 and 77) in one direction in accordance with the characters represented by each wire 78. These character wires 78 are extensions of the leads of the character diodes of character matrix 15. If, for example, the character presented in coded form at code input 10 represented the letter B, AND-gates 83 and 84 (FIG. 2) are energized. Gated amplifiers 85 and 86 then, upon occurrence of trigger pulses over matrix trigger wire 67, pass a large pulse of current through diode 82 and lead 78a of character matrix 15. The lead 78a is threaded through cores 75, 76, and 77 and, in addition, is threaded through all of the other ferrite cores of dot core array 16 that are used in the synthesis of the letter B. Therefore, when the large pulse of current passes through diode 82, it also passes through lead 78a which is threaded through all of the B cores and thus sets to their one state all of the cores used to synthesize a B. According to the right-hand rule of magnetic induction, a magnetic flux is thus induced to flow in cores 75, 76, and 77 in the direction of the arrow in response to the current pulse passing through wire 78a. At the proper time for core 75 to be interrogated, in order to deflect the stream of ink droplets to the location of the dot to be generated by core 75, a large pulse of current is sent through reset wire 90 and diode 91. It can be seen from FIG. 8 that this pulse of current, passing through reset wire 90 and diode 91, induces a flux to flow in core 75 in the opposite direction from the flux induced by the current pulse through wire 78a. This causes a reversal of the flux flowing through core 75, thus resetting core 75 to its zero state. This flux reversal induces a voltage pulse across read-out wires 95, 97, and 98 which are threaded through core 75.

Read-out wires 95, 97, and 98 are selected ones of a complete set of read-out wires comprising wires 92 to 98, inclusive. Those read-out wires 95, 97, and 98 passing through core 75 carry the voltage impulses, generated by the flux reversal of ferrite core 75, to suitable utilization devices. The unselected read-out wires 92, 93, 94, and 96 carry no voltage pulses to their associated utilization devices at the time core 75 is interrogated since they do not pass through ferrite core75.

The permutation of pulses appearing on wires 92 to 98 and forwarded to the utilization devices determines the deflection voltages to be applied to the deflection electrodes of the device disclosed in the patent to C. R. Winston mentioned hereinbefore. Wires 92 to 98 are thus selectively wired through all of the dot cores in core array 16 in different patterns to generate permutations corresponding to the ditferent vector locations of the several dots to be printed.

Each of the ferrite cores of dot core array 16 corresponds to a directed line segment or vector of the trace pattern of the particular dot within a character to which the core corresponds. Thus, core 75, for example, represents the vector beginning at the lowermost dot in the third column of dots counting from the left edge of the character, dot 99 in FIG. 9. The code generated in wires 92 to 98 by core 75, directs the jet of ink droplets to the adjacent dot 100 of the next column of dots in FIG. 9, the end of the vector. Therefore, while dot 99 is being printed, a pulse passes through wire 90 and diode'91, which are the wire and diode corresponding to the location of dot 99, to read out or reset core 75 and generate a permutation signal on read-out wires 92 to 98 which directs the jet of ink droplets to dot 100. FIG. 9 shows the letter B in a prone position to correspond to dot matrix 21 of FIG. 5.

It can be seen that this movement of the stream of ink droplets from dot 99 to dot 100 is not accomplished solely in the letter B but also in the letters D, E, F, K, L, and others. Therefore, in addition to the B wire 98a and B diode 82, wires 78b to f, inclusive, and associated diodes are shown as part of the group of character wires 78 passing through the core 75, the others being omitted here for clarity. Therefore, whenever a B, D, E, L, F, or K, etc., is presented at code input 10, core 75 is set to its one state. And when core 75 is in its one state, and the stream of ink droplets is printing the dot 99, a

current pulse passing through wire 90 and diode 91 resets core 75 to its zero state, generating the deflection permutation signals on read-out wires 92 and 98 which deflect the stream of ink droplets to dot 100. Wire 90 passes through all of those cores in dot core array 16 which could possibly be reset during the printing of dot 99, but in the case of the letter B, only core 75 is in its one state. As a consequence, the other cores through which reset wire 90 passes, are in their zero states and Will generate no pulses on wires 92 to 98 for the letter B. The cores 76 and 77 correspond to other vectors extending from other dot positions in the letter B (and some other letters) and are reset by current pulses passing through the diodes 186 and 192 during the printing of the dots which correspond to the beginning of the desired vectors.

In the interrogation procedure just described, it should be noted that all of the ferrite cores in the matrix 16 associated with the same dot location are simultaneously supplied with an interrogation pulse of current passing through the reset wire and diode of the matrix 21 associated with that dot location. But, as stated previously, only one out of this plurality of cores previously has been set to its one state in accordance with the particular character to be decoded; and all of the other cores representing different vectors extending from that dot location remain reset to their zero state and are unaffected by the interrogation pulse. As a consequence, only a single permutation-coded new dot output indication is obtained on the readout wires 92 to 98, and this output indicates the location of the next dot in the sequence and is decoded in the matrix 21 to initiate interrogation of the next dot in the sequence for the particular character being synthesized.

The operation of the interrogation procedure and manner in which the vector location for the next succeeding dot location is obtained by interrogating the dot location presently being synthesized may be better understood by referring to a specific example in which different characters employ printing of the same dot in one position followed by the printing of a different dot position depending upon which of the characters is being synthesized. The letters T, I and E all use the same dot located at the crosspoint of the T, the upper crosspoint of the I and located near the midpoint of the upper horizontal bar of the letter B. For purposes of illustration, assume that this is the dot presently being printed in all three of these characters and that for the letters T and I, the next dot location should be the dot immediately below this dot and for the letter E should be the dot immediately to the right on the same horizontal line.

If the letter T or the letter I is being synthesized or generated, the ferrite core in the matrix 16 for that dot location which has been set by the output of the character matrix 15 is the core which is wired to provide an output indicative of the vector terminating in the next lower dot in the vertical direction. When letter E, however, is being synthesized, a different ferrite core, also associated with that same dot position, but wired to provide an output indicative of the next dot position to the right is the core which has been selected or set by the output of the character matrix 15. The interrogation pulse obtained from the diode matrix 21 passes through both of these cores associated with that dot position (and also passes through any other cores associated with that same dot position); but since only a single core for any dot position is set to its one state for a particular character, only that core will be reset providing output signals on the output windings 92 to 98, thereby controlling the location of the next dot position to be interrogated. The fact that the reset pulse also passes through other cores associated with the same dot position has no effect on the output windings, since these other cores already are reset to their zero state and produce no change in flux which can induce signals on the output windings 92 to 98.

As a consequence, the production of the crosspoint of the letter T or the cross point of the letter X is no more difficult to implement than the production of the next line segment along a straight line such as found on the upper horizontal bar of the letter E. The number of cores used in the matrix 16 for each dot location depends on the number of different vectors which are necessary to form the particular symbols which the system is programmed to generate and this number will vary accordingly. These vectors are not limited to vectors extending to adjacent dots, but can extend from any location in the output matrix to any other location.

Read-out wires 92 to 98 are connected to read-out amplifiers 102 and 108, respectively (FIG. 4), and the pulses generated on read-out wires 92 to 98 are amplified by read-out amplifiers 102 to 108 which drive individual binaries of a shift register 110.

Bistable multivibrator At this point, there will be described the operation of the individual binary or bistable multivibrator used in shift register 110 and elsewhere within the character synthesis system. FIG. 10 shows a schematic diagram of a typical bistable multivibrator suitable for use in this character generation logic system. The emitters of two transistors and 121 are connected to one end of a resistor 122. Conventional feed-back voltage dividers are provided from the collector of each transistor to the base of the other transistor. Switching of the bistable multivibrator is accomplished by a positive-going transition in the voltage level of the condition appearing at any one of four possible trigger inputs 125 to 128. If the bistable multivibrator is already in the state desired, no change occurs; but if the bistable multivibrator is in the opposite condition, the voltage transition appears at the base of the then-conducting transistor in the form of a positive voltage pulse and drives the then-conducting transistor into its cutoff region. The positive-going transitions pass through capacitors to 133 and blocking diodes 135 to 138, respectively. Since the character-generating system contemplates the use of many inputs on each bistable multivibrator and since it is desirable that not all trigger pulses be capable of triggering the bistable multivibrator, a gating or priming circuit is provided for each trigger input 125 to 128. The priming inputs to 143 cooperate with their associated capacitors to provide RC coupling networks.

Referring specifically to the gate comprising terminals 125 and 1-40, for example, when a voltage input of -6 volts is provided at terminal 125, as well as at terminal 140, there is no voltage difference across the capacitor 130 and 6 volts appears at the anode of blocking diode 135. When a positive-going transition from --6 volts to 0 volt is provided at terminal 125, 0 volt appears at the anode of blocking diode 135. This is inadequate to pass a current pulse through blocking diode 135 to drive transistor 121 into its out off region. If, however, terminal 125 is maintained at 6 volts and terminal 140 is maintained at 0 volt, a voltage difference of 6 volts appears across capacitor 130 and the anode of blocking diode 135 is maintained at 0 volt. When terminal 125 is suddenly changed to 0 volt, the voltage difference across capacitor 130' cannot be altered instantaneously; and +6 volts appears at the anode of blocking diode 135. Since blocking diode 135 cannot support a positive anode-to-cathode voltage, it conducts a current pulse, overcoming the feed-back biasing circuit of the base of transistor 121, driving transistor 121 deep into its cut-off region.

Since the gating arrangement between terminals 125 and 140 is capacitive and resistive in nature, it results in a capacitor-storage of the previously applied priming. voltage, which lasts for a few microseconds. A delay is thus experienced in establishing a new voltage difference across capacitor 130; therefore, a sudden change of priming input voltage at terminal 140 has no instantaneous effect upon the gating network. If a voltage change at the priming input 140 occurs simultaneously with a trigger signal (positive voltage transition) at terminal 125, the new priming voltage at terminal 140 is ineffective to determine whether or not transistor 121 is to be cut off; and the prior priming condition of terminal 140 therefore prevails.

By supplying a conjugate pair of signal-carrying :wires to terminals 140 and 142, the bistable multivibrator of FIG. 10 is made to assume that signal condition of the conjugate pair of wires when a trigger pulse is received at both terminals 125 and 127. Only the trigger signal reaching a primed volt) gate 'will pass through the associated blocking diode. Any gate can be permanently primed so that any trigger pulse received by the gate will be passed through the associated blocking diode.

Similar gates are used at the inputs of the two monostable multivibrators 148 and 149 of the local clock 20 of FIG. 3. When bistable multivibrator 147 is set to its one state by a clock pulse from timing input 13' passing through inhibit gate 17, bistable multivibrator 147 sends a trigger pulse (positive-going transition) to continuouslyprimed trigger input 152 of monostable-multivibrator 148, setting it to its quasistable state. The steady state (0 volt) of this pulse from bistable multivibraor 147 then primes priming input 153 of another gate of monostable multivibrator 148. After a predetermined delay, monostable multivibrator 148 returns to its stable state and sends a trigger pulse (positive-going transition) over wire 150 and also triggers monostable multivibrator 149 through a continuously primed trigger input 154. After the predetermined interval of monostable multivibrator 149, it returns to its stable state and sends a trigger pulse over wire 151 and also triggers monostable multivibrator 148 through trigger input 155 of the gate primed at priming input 153 by bistable multivibrator 147. Therefore, as long as bistable multivibrator 147 stays in its one state and primes monostable multivibrator 148 at priming input 153, local clock 20 will continue issuing local clock timing pulses on =wires 150 and 151. *Each predetermined interval of one monostable-multivibrator constitutes a half-cycle of local clock 20.

Deflection signal generation Wires 92 to 98 of FIG. 8 are so connected to amplifiers 102 to 108 shown in FIG. 4 that the permutation signals appearing on wires 92 to 98 are suitably amplified and used to drive their associated bistable multivibrators 112 to 118 of buffer storage register 110. The permutationcoded signals obtained from the output stage of the buffer storage register 160 are supplied over leads 23 to the deflection circuits and also are supplied in parallel to the dot matrix 21 to prepare the matrix 21 for interrogation of the core of the dot core array 16 which is associated with the dot being printed. Buffer storage register 1 is reset by the local clock pulse appearing on wire 151 at every cycle of local clock 20 so that each bistable multivibrator 112 to 118 is in its zero state prior to the interrogation of the next core of the dot core array 16. When the core interrogated by operation of an interrogation pulse through the selected diode of the matrix 21 is reset, the permutation signal generated on wires 92 to 98 sets, to their one state, those bistable multivibrators 112 to 118 of buffer storage register 110 that are associated with the particular Wires 92 to 98 which are threaded through the core just reset. For example, in FIG. 8 wires 95, 97 and 98 are threaded through core 75; and when core 75 is reset to its zero condition, wires 95, 97, and 98 carry voltage pulses to their associated amplifiers 105, 107, and 108 of buffer storage register 110 while wires 92, 93, 94, and 96 of FIG. 8, which are not threaded through core 75, carry no pulses under these conditions. Amplifiers 105, 107, and 108 then issue trigger pulses which are carried to continuously primed trigger inputs of the multivibrators 115, 117, and 118 of buffer storage register setting bistable multivibrators 115, 117, and 118 to their one state while the other multivibrators of buffer storage register 110 remain in their zero state having received no trigger pulses. A conjugate pair of outputs is taken from each of the bistable multivibrators 112 to 118 of buffer storage register 110, each pair of outputs containing one output at 0 volt (one state) and another output at -6 volts (zero state). These outputs are used to prime the input gates of the bistable multivibrators of a shift register 160.

Referring now, for example, to bistable multivibrator which is in its one state as a result of the resetting of core 75, wire is now at 0 volt and wire 171 is now at 6 volts. Conversely, bistable multivibrator 114 of buffer storage register 110 is in its zero state since it did not receive a voltage pulse over wire 94 from the resetting of the core 75. Output wire 172 of bistable multivibrator 114 is at 0 volt and output wire 173 is at -6 volts. Wires 170 and 171 are thus priming bistable multivibrator 165 of shift register 160 to assume its one state as soon as a trigger pulse is provided to its trigger inputs. Conversely, output wires 172 and 173 are priming bistable multivibrator 164 to its zero state.

When a trigger pulse passes wire 151 from local clock 20, it is suitably amplified by amplifiers 175 and 176. The output from amplifier 176 passes through OR-gate 177 and triggers each of the bistable multivibrators of shift register 160 to assume that state to which it is primed by its associated bistable multivibrator of buffer storage register 110. The pulse issuing from amplifier 175 simultaneously resets all of the bistable multivibrators 0f register 110 to their Zero state preparing register 110 for the interrogation of the next core. Due to the resistive-capacitive nature of the input gates of the bistable multivibrators of shift rgister 160, these gates possess a capacitively-stored priming feature which permits the priming condition to persist for a few microseconds after the change of the priming voltage level; thus, the bistable multivibrators of shift register 160 assumes the previous state of their associated bistable multivibrators of register 110 in spite of the fact that all of the bistable multivibrators of register 110 are reset to their zero states simultaneously with the triggering of the bistable multivibrators of shift register 160.

The outputs from shift register 160 are used to energize the deflection circuits 24 in order to operate the ink transferring device disclosed in the patent to C. R. Winston mentioned above, and these outputs from shift register 160 are also used to determine which of the dot cores in core array 16 will be reset next. Location code wires 180 carry the pairs of signals taken from the bistable multivibrators of shift register 160 and deliver these signals to two sets of AND-gates 181 and 182 which are otherwise similar to AND-gates 12a and 12b of FIG. 2.

Since, in the example under consideration, the outputs from shift register 160 presently deflect the beam of ink droplets to dot location 100 in FIG. 9 after the resetting of core 75, it is necessary to select the next vector extending from dot location 100 at this time. A dot matrix 21 is used to effect this selection, and the matrix 21 includes a selection diode corresponding to each possible dot location in the character matrix employed. Thus, in the example under consideration, using a seven by ten matrix, seventy diodes corresponding to seventy dot locations are employed. The leads connected to each of these diodes pass through all of those cores in the dot core array which correspond to the dot locations which possibly could follow the particular dot location represented by each diode. Thus, there is present in dot matrix 21 a single diode 186 which corresponds to dot location 100 of FIG. 9. Diode 186, upon the energization of AND-gates 183 and 184 and the issuance of a clock pulse over wire 150 from local clock 20 to gated amplifiers 185, conducts a large pulse of current through its lead which passes through the core 76 and all of the other cores corresponding to possible dot locations which could follow location 100. Of these cores, only core 76 previously has been set to its one state for the letter B in the example under consideration. For different characters, a different core representing a different vector extending from dot location 100 could be reset. Since diode 186 is the reset diode, the lead to which passes through core 76 of FIG. 8, this large pulse of current through 186 resets core 76 to its zero state generating pulses of current over wires 95, 96, and 98 threaded through core 76. In response to the pulses thus appearing on wires 92 and 98 amplifiers 105, 106, and 108 issue trigger pulses to bistable multivibrators 115, 116, and 118 of buffer storage register 110. Upon the next half cycle of local clock 20, the pulse issuing on wire 151 transfers the information from register 110 to shift register 160 and simultaneously clears register 110.

Bistable multivibrators 165, 166, and 168 are now in their one state while the remaining bistable multivibrators of shift register 160 are in their zero state. This condition passes over wires 23 and deflects the beam of ink droplets to dot location 191 of FIG. 9 by means of the deflection circuits shown in greater detail in FIG. 11. This same signal passing over wires 180 energizes AND-gates 183 and 188. One-half cycle later, local clock 20 issues a trigger pulse over wire 150 which triggers gated amplifier 190 permitting amplifier 189 and gated amplifier 190 which are associated with AND-gates 188 and 183, respectively, to place a large pulse of current through diode 192.

Diode 192 corresponds to dot location 191 in FIG. 9, and the elongated leads of diode 192 pass through all of those cores of dot core array 16 which correspond to the dot locations which could possibl follow dot location 191 in any character in the type font. However, only one of these cores, core 77, through which the leads of diode 192 are threaded has been set to its one state by the B wire 78a of diode 82 of the character matrix and only core 77 will be reset from its one state to its zero state by the pulse of current passing through the diode 192. Wires 94, 95, 96, and 98 pass through core 77 and thus carry a voltage pulse when core 77 is reset. The permutation signal thus carried by wires 92 to 98 and which ultimately is stored in the flip-flops 162 to 168 deflects the stream of ink droplets to dot location 193 in FIG. 9. Dot location 193 could follow dot location 191 in the synthesis of the characters B, D, E, F, T, and Z, but not the characters K and L. Cores 75, 76, and 77 were described above as having been so wired.

Shift register 160 is triggered once for each dot printed and oncemore when the last core in the sequence is interrogated, in order to deflect the stream of ink droplets to an idle position out of the printing field. The letter B (FIG. 9) is made up of thirty-one individual dots; therefore, to print the letter B, shift register 160 must be triggered at least thirty-two times.

Deflection delay In the ink transferring device disclosed in United States Patent 3,060,429, granted to C. R. Winston on Oct. 23, 1962, an ink droplet traveling from nozzle 13 to platen 11 in that patent requires a finite length of time to traverse this distance. The vertical deflecting electrodes 42 and 43 of the Winston patent are positioned closer to the nozzle 13 than are the horizontal electrodes 44 and 45 in FIG. 5 of the Winston patent. Therefore, an ink droplet proceeding from nozzle 13 of the Winston patent passes between vertical deflection electrodes 42 and 43 before it passes between horizontal deflection electrodes 44 and 45. In order to prevent smearing of the dots with which a character is formed, a change in the deflection signal applied to vertical deflection electrodes 42 and 43 must precede a change in horizontal deflection signal applied to horizontal deflection electrodes 44 and 45 of the Winston patent. This time diflerence between the changes applied to the keep the same average electrode two sets of deflection electrodes must be equal to the time required for an ink droplet to proceed from the vertical deflection electrodes to the horizontal deflection electrodes so that the change in deflection signals applied to these two sets of electrodes will affect the same droplet initially. Thus, the first droplet passing through vertical deflection electrodes 42 and 43 after a change in vertical deflection signal will also be the first droplet passing between horizontal deflection electrodes 44 and 45 of the Winston patent after a change in horizontal deflection signal.

Referring now to FIG. 4, bistable multivibrators 165, 166, 167, and 168 carry the vertical deflection signal and are connected directly to the deflection circuits 24 over wires 195 of wires 23. On the other hand, bistable multivibrators '162, 163, and 164 carry the horizontal deflection signal and are not connected directly to the digital-toanalog converter but are used instead to prime an additional shift register 200. The priming and triggering of shift register 200 is similar to the priming and triggering of shift register with the exception that the trigger pulse issuing from OR-gate 177 does not immediately trigger the bistable multivibrators of shift register 200. Instead, the pulse issuing from OR-gate 177 triggers a monostable multivibrator 205 to its quasistable state; thus, the clock pulse issuing from OR-gate 177 triggers each bistable multivibrator of shift register 160 to assume the state of its associated bistable multivibrator of bufler storage register 110 and also triggers monostable multivibrator 205 to assume its quasistable state. At this point in time, the vertical deflection signals from bistable multivibrators 165, 166, 167, and 168 pass immediately over wires to the vertical ,digital-to-analog converters of deflection circuits 24 (FIG. 1) to generate the deflection voltages while the outputs from bistable multivibrators 162, 163, and 164 merely prime the inputs to the bistable multivibrators of shift register 200.

After the predetermined delay of monostable multivibrator 205 has elapsed, this monostable multivibrator returns to its stable state sending a trigger pulse to all of the bistable multivibrators of shift register 200 setting them to the state to which they were primed by bistable multivibrators 162, 163 and 164 of shift register 160. The outputs of shift register 200 then proceed over wires 206 of wires 23 to the horizontal digital-to-analog converters of deflection circuits 24 to generate the horizontal deflection voltages. Wires 23 from FIG. 4 are continued in FIG. 11 wherein wires 195 are shown going to the two vertical digital-to-analog converters 208 and 211, and wires 206 are shown as being connected to the two horizontal digital-to-analog converters 212 and 213.

Half of wires 206 connect digital-to-analog converter 2-12 to the lower output terminals of the bistable multivibrators of shift register 200; and the other half of wires 200 from the upper output terminals of these same bistable multivibrators carry signals of the opposite binary sense or polarity to digital-to-analog converter 213. Since digital-to-analog converter 212 drives horizontal deflection electrode 44 of the Winston patent (also shown in 11) through a suitable amplifier 214 herein and digital-to-analog converter 213 drives horizontal deflectron electrode 45 of the Winston patent through a suitable amplifier 215 herein, digital-to-analog converter 212 must develop a discrete voltage output equal to and opposite from the discrete voltage output developed by digital-toanalog converter 213. These discrete voltages are then added to the average voltage of horizontal deflection electrodes maintained by amplifiers 214 and 215 in order to voltage at the horizontal deflection electrodes, but to maintain a voltage difference between the two horizontal deflection electrodes to deflect the stream of ink droplets. These opposite but equal, discrete voltage levels are obtained by driving the two digital-to-analog converters 212 and 213 by signals of the same but opposite binary sense.

Digital-to-analog converter 212 is drawn in greater detail in order to show the details of its operation. In converting from a digital to an analog signal, the permutation code digital input comprises several separate input wires maintained at one or the other of two voltages. In determining the output voltage level, some of the inputs must be given greater weight than others. This is accomplished by connecting a resistor in series with each input wire. The input wire to be accorded the greatest weight is connected to the lowest resistance R in order to pass the greatest amount of current for the given voltage of the binary input signals. The input having one-half as much weight is connected through a resistor of twice the resistance 2R in order to pass half as much current in response to the same voltage of the binary input signal. The output voltage to amplifier 214 is then proportional to the current flowing through the output resistor R The digital-to-analog converters 208 and 211 provide opposite but equal discrete voltage levels to the vertical deflection electrodes 42 and 43 in a manner which is described in detail in a subsequent section.

End-of-character and reset In the generation or synthesis of a character, the last core of dot core array 16 to be reset must indicate to the system that a character is at an end. All of those cores of dot core array 16 which are the final cores in any given sequence of a character in the type font have wired through them a single stop wire 220 (FIG. 4) instead of permutations of wires 22 to 98. Therefore, while the last dot of the character is being printed, the diode in diode matrix 21 which corresponds to that dot location, passes a large pulse of current and resets the final core in the sequence to its zero state. This core, in resetting to zero, generates a voltage pulse on wire 220. The voltage pulse on wire 220 is suitably amplified by amplifier 22-1 and sets bistable multivibrator 222 to its one state. At the same time, this amplified pulse issuing from amplifier 221 passes over wire 223 and resets bistable multivibrator 147 (FIG. 3) to its zero state removing the priming condition from priming input 153 of monostable multivibrator 148 of local clock 20. The voltage pulse generated on wire 220 is generated in response to the pulse issuing from local clock 20 on wire 150; therefore, it can be seen that with the priming condition removed from priming input 153, the next pulse issuing from local clock 20 over wire 151 will not trigger monostable multivibrator 148 at its trigger input 155; thus, breaking the loop of operation and turning off local clock 20. This last pulse on wire 151, however, resets bistable multivibrator 222 to its zero state and simultaneously sets bistable multivibrator 224 to its one state as it is primed by bistable multivibrator 222.

Since this last core did not set any of the bistable multivibrators of shift register 110 to their one state, shift register 160 is now completely idle with all of the bistable multivibrators of shift register 160 in their zero state. This condition is conducted over wires 23 to the deflection circuits operating the deflection electrodes, in order to deflect the stream of ink droplets downwardly below the normal printing field and onto a mask placed in front of the paper in order to prevent spurious ink marks on the paper. When bistable multivibrator 224 is in its one state, it primes gated amplifier 225. After monostable multivibrator 205 has timed its predetermined interval, it sends a pulse over wire 226 to trigger gated amplifier 225 sending a pulse over spacing wire 227 to effect spacing of the printer.

When shift register 160 is in its idle condition it selects AND-gates 182 and 230 (FIG. The selection of these two AND-gates conditions dot matrix 21 to pass a pulse of current through diode 231 by triggering the gated amplifier associated with AND-gate 230 upon the issuance by local clock 20 of a pulse on wire 150 at the beginning of the next character. The elongated leads of diode 231 pass through all of those cores of dot core array 16 which could possibly be the first core of any character. Therefore, as soon as the next pulse is presented to timing input '13 starting local clock 20, the first pulse issuing from wire 151 starts the sequence of character generation, resetting the first core in the sequence by a large pulse of current through diode 231. In addition, the pulse applied to timing input 13 also passes over wire 235, through OR- gate 177 to reset shift register to assure that shift register 160 is in its idle condition and also to reset bistable multivibrator 224 to its zero condition in response to the zero condition of bistable multivibrator 222. At this point, the character synthesis system is prepared to begin the next character.

Spacing Since there are forty nozzles across the width of the printer and each nozzle can print to the left or to the right, controls must be provided for determining which nozzles are emitting ink, which nozzle is printing, and whether it is printing to the left or to the right.

As described previously, at the end of one charactercycle of operation of the synthesis system, a pulse issues from gated amplifier 225 over spacing wire 227 in order to initiate spacing or column selection of the printer. This spacing signal passes through OR-gate 239 (FIG. 6) and triggers bistable multivibrator 240. Bistable multivibrator 240 is arranged to reverse its condition upon receipt of a trigger pulse from OR-gate 239 and therefore acts as a single-stage binary counter. The outputs of histable multivibrator 240 are used to control the horizontal deflection of that stream of ink droplets that is printing at any given time in order to determine whether or not the stream is printing to the left or to the right of the nozzle center line. In order to determine whether the printing nozzle is deflected to the right or to the left of the nozzle center line, two outputs of opposite binary polarity are taken from bistable multivibrator 240 and are carried over wires 236 and 237. These outputs are shown in FIG. 11 going to digital-to-analog converters 212 and 213 to impart the major left-right swing to the stream of ink droplets. In the detail of digital-to-analog converter 212, wire 236 is shown delivering one or the other of the two binary voltages through the lowest resistance /2R into digital-to-analog converter 212 in order to have the greatest weight in determining the level of the deflection voltage going into amplifier 214. After the left-hand character has "been completed, the pulse traveling over wire 277 triggers bistable multivibrator 240 which in turn determines that the next character printed by the ink transferring device will be printed to the right of the nozzle center line. After this right-hand character has been completed, another pulse on wire 227 triggers bistable multivibrator 240 to again change its condition and to determine that the succeeding nozzle prints the next character to the left of its center line, as will be described.

In order to space the printer without printing a character, a spacing function character is provided at code input 10 and is recognized by AND-gate 40. AND-gate 40 primes gated amplifier 42 so that when a timing signal is received at timing input 13, this timing signal travels over wire 47 and triggers gated amplifier 42. Upon being triggered, gated amplifier 42 sends a pulse over wire 232 to trigger .monostable multivibrator 233 to its quasistable state. After the predetermined duration of monostable multivibrator 233, it returns to its stable state and sends a pulse over wire 234 to trigger bistable multivibrator 240 through OR-gate 239. The purpose of the delay of monostable multivibrator 233 is to provide the spacing trigger pulse to bistable multivibrator 240 over wire 234 at about the same time as a pulse would be sent over wire 227 if a character had been printed.

Another output of bistable multivibrator 240 is carried on wire 241 and is used to similarly trigger another bistable multivibrator 242 to assume its operation condition after each complete excursion of bistable multivibrator 240. Since the outer two streams of ink droplets are always deflected downwardly onto the mask while the center stream is printing, in the preferred embodiment of the invention, the discrete vertical deflection signal issuing from vertical digital-to-analog converters 208 and 211 are used at any given time to drive only half of the forty ink transfer devices used in the page printer. Of these twenty ink transfer devices driven at any given time, ink is issuing from only one; therefore, only that one is printing. Alternate pairs of vertical deflection electrodes are driven together by the vertical digital-to-analog converters 208 and 211; thus, all of the even-numbered pairs of vertical deflection electrodes are driven together, and all of the odd-numbered pairs of vertical deflection electrodes are driven together. Bistable multivibrator 242 determines whether the even-numbered or the odd-numbered vertical deflection electrodes respond to the signals carried on wires 195 and that the non-responding vertical deflection electrodes direct their associated streams of ink droplets downwardly onto the mask.

In order to determine which sets of deflection electrodes receive character-generating signals, two outputs of opposite binary polarity are taken from bistable multivibrator 242 and are carried over wires 2.44 and 245. These Wires are shown in FIG. 11 as conducting these signals to suitable amplifiers 246 through 249. When wire 245 carries volt (one state), amplifiers 247 and 249 amplify and conduct deflection signals from digital-to-analog converters 208 and 249 to the vertical deflection electrodes of the ink transfer device of the Winston patent reproduced in FIG. 11. The same signals are carried to alternate ones of the other ink transferring devices, none of which are emitting ink. Since wire 244 carries 6 volts (zero state), amplifiers 246 and 248 determine that the vertical deflection electrodes of the ink transferring devices to which amplifiers 2 46 and 248 are connected deflect those of their associated streams of ink droplets that are flowing, downwardly onto the mask placed below and in front of the paper. Since each nozzle prints two adjacent characters, a change of vertical deflection amplifiers is accomplished only after the printing of every second character. The output of bistable multivibrator 240 on wire 241 is also amplified by amplifier 243. The output of amplifier 243 is used to turn on the next stream of ink droplets to the right and to turn off the last stream of ink droplets to the left; thus, stepping the on condition of the nozzles one step to the right. In order to turn on three of the forty jets required to print across a page, it is necessary that the valving electrodes of each nozzlecorrespending to the control grids of cathode-ray tubes-be maintained at one or th other of two voltages, on voltage or an off voltage. This can be done by the use of a 40-stage ring counter with the count advancing through the ring counter with three adjacent elements on at once. In order to conserve over half of these expensive ring counter elements, a matrix format has been devised with AND-gates at the junction points of the matrices. The inputs of these matrices are provided by similar but smaller ring counters, the first of which comprises bistable multivibrators 250 and 257. Three adjacent bistable multivibrators are in their one state at any given time. The output of each element of this ring counter primes the next element in the ring and all elements are triggered simultaneously by the trigger pulse issuing from amplifier 243 in order to advance the three one states one step in the ring. Bistable multivibrator 257 primes bistable multivibrator 250 in order to keep the three one states circulating. Another ring counter is provided which comprises bistable multivibrators 260 to 264. The outputs of these bistable multivibrators coact with the outputs of bistable multivibrators 250 to 25 3 to provide inputs to the first matrix 275 of two matrices of AND-gates. A third ring counter comprising bistable multivibrators 265 to 269 coacts with bistable multivibrators 254 to 257 of the first ring counter to provide the inputs of the second matrix 276 of AND-gates.

In order to begin a spacing operation at the left-hand margin of a page, a carriage-return signal is received at AND-gate 50 in FIG. 1. The pulse issuing from gated amplifier 51 passes over wire 52 and resets all three ring counters to their initial condition by triggering bistable multivibrators 250, 251, 252, 260, and 265 to assume their one state and by triggering bistable multivibrators 253, 254, 255, 256, 257, 261, 262, 263, 264, 266, 267, 268, and 269 to assume their zero state. With the three ring counters in this conditon, AND-gates 280, 281, and 282 of AND-gate matrix 275 are selected. These selected AND-gates provide on voltage to their associated outputs 285, 286, and 287 that are in turn connected to the control or valving electrodes of the leftmost three nozzles 291, 292, and 293 which are shown in FIGS. 6 and 11 along with several other of the valving electrodes to illustrate the relationship between the column selector circuits and the ink transferring device of the Winston patent.

In the leftmost condition, the nozzle associated with AND-gate 280 is a dummy, provided only to balance the electrostatic field for the nozzle associated with AND-gate 281 which is now prepared to print a character. The nozzle associated with AND-gate 282 is the next nozzle to print after the nozzle of AND-gate 281 has completed printing its right-hand character. After the nozzle of the AND-gate 281 has printed its right-hand character, the pulse appearing on wire 227 triggers bistable multivibrator 240 to cause the horizontal deflection amplifier system to print the left-hand character. Bistable multivibrator 240 triggers bistable multivibrator 242 to interchange the function of the two vertical amplifier systems. This same pulse passes through amplifier 243 and triggers all of the bistable multivibrators 250- 257 of the first ring counter. Each bistable multivibrator assumes the condition of the preceding bistable multivibrator. Therefore, bistable multivibrators 251, 252, and 253 are now in their one state energizing AND- gates 281, 282, and 283. After the nozzle of AND-gate 282 prints its left-hand character and then finishes printing its right-hand character, the first ring counter advances one step and energizes AND-gates 282, 283, and 284. As characters are printed across the page, the first ring counter continues to advance; and when bistable multivibrators 254, 255, and 256 are all energized, bistable multivibrator 253, upon changing state from one to zero, sends a trigger pulse over wire 290 to advance the energized condition in the second ring counter from bistable multivibrator 260 to bistable multivibrator 261. This prepares the second column of the first matrix 275 for operation while operation of the printer continues to be controlled by the first column of the second matrix 276. In a similar manner, when bistable multivibrator 257 changes state from one to zero, bistable multivibrators 250, 251, and 252, are set to the one" state, and a trigger pulse is supplied to the third ring counter to advance the energized condition in the counter from bistable multivibrator 265 to bistable multivibrator 266. Thus, control of the printing positions then is being effected through the AND-gates in the second columns of the matrices 275 and 276. The ring counters continue to cycle from row to row and column to column in this manner until another carriage return character is received att he code input 10 resetting the three ring counters to their original condition.

In order to provide the page printer with an automatic carriage return and line feed system, outputs from suitable ones of the bistable multivibrators of the three ring counters can readily be combined in an AND-gate which can be used to energize the resetting system in parallel with the carriage return AND-gate 50 and can also energize the line feed mechanism 57.

Although only one embodiment of the invention is shown in the drawings and described in the foregoing specification, it will be understood that invention is not limited to the specific embodiment described, but is capable of modification and rearrangement and substitution of parts end elements without departing from the spirit of the invention.

What is claimed is:

1. An electronic circuit for symbol synthesis wherein a symbol is formed by generating a sequence of visible dots in a matrix of dot locations comprising:

a plurality of control means, each means individual to a dot in the sequence of dots required to define the symbol to be synthesized, for determining the location of the dots in the symbol;

means for applying, at the time of generation of each dot in the symbol, a signal to the control means individual to said dot; and

means responsive to the application of said signal to said control means for producing a digital representation of the location of the next dot to be generated in the sequence of dots required to define the symbol.

2. An electronic circuit for symbol synthesis wherein symbols are formed by generating a sequence of visible dots in a matrix of dot locations comprising:

means for representing each of the symbols which the circuit is capable of synthesizing, said representing means being adapted to be energized;

a plurality of memory elements each individually associated with a dot of the matrix required to define the different symbols represented by the symbol representing means selected memory elements arranged for energization upon energization of each symbol representing means, only one memory element for any given dot location being capable of energization by the energization of a symbol representing means;

means for energizing a symbol representing means; means individually associated with each dot location of the matrix required to define the symbol represented by the energized symbol representing means for interrogating the memory elements associated with the same dot location as the dot interrogating means upon application of a signal to the dot interrogating means;

means for applying, at the time of the generating of each dot in the symbol, a signal to only the dot interrogating means associated with the location of that dot whereby the associated energized memory element corresponding to that dot location of the selected symbol is interrogated; and

means responsive to the interrogation of each energized memory element for generating a first and second series of control signals which comprise a two-dimensional digital representation of the location of the next dot in the sequence required to define the symbol.

3. A circuit according to claim 2 wherein said memory elements are ferrite cores.

4. A circuit according to claim 3 wherein the symbol representing means and the interrogating means are conductors threaded through said ferrite cores and wherein the generating means comprises a plurality of conductors selectively passing through said ferrite cores.

5. Apparatus for sequentially synthesizing a symbol and printing that symbol sequentially in a t-wo-dimensional matrix of dot locations in response to a permutation code comprising:

means for generating a single representation of the symbol to be printed, in response to receipt of a permutation code combination individual to that symbol;

means for setting a plurality of memory elements in response to the single representation thus generated;

means for detecting the condi ion of a h m mory element in a variable sequence determined by the locations of the dots in the symbol; and

means for printing a dot at each dot location as determined from the detecting of the condition of each memory element.

6. An electronic circuit for symbol synthesis wherein symbol is formed by generating a sequence of visible dots in a matrix of dot locations comprising:

a symbol conductor representing one of the symbols that the circuit is capable of synthesizing;

means for supplying a signal through the symbol conductor;

a plurality of memory elements each individually associated with a dot location of the matrix required to define the one symbol represented by the symbol conductor, the memory element being energized by passage of a signal through the symbol conductor with only a single memory element being energized for any dot location;

a matrix having a plurality of matrix elements individually assocated with a dot location for all symbols be synthesized; with passage of a signal through an element of the matrix interrogating the memory elements associated with the same dot as the matrix element;

means for passing, at the time of the generating of each dot in the symbol, a signal through the matrix element associated with the location of that dot whereby the assocated energized memory element is interrogated; and

means responsive to the interrogation of each energized memory element for generating a first and second series of control signals which comprise a two-dimensional digital representation of the location of the next dot in the sequence required to define the symbol.

7. An electronic circuit for symbol synthesis wherein a symbol is formed by generating a sequence of visible dot in a matrix of dot locations comprising:

a local clock-pulse generator;

a plurality of control conductors, each conductor individual to a dot in the sequence of dots required to define the symbol to be synthesized;

means for applying, in response to a local clock pulse, a signal to the control conductor individual to a first dot then being generated;

means responsive to the presence of said signal on said conductor for producing a first and second series of control signals in a two-dimensional, digital representation of the location of a second dot in the sequence of dots required to define the symbol; and

means responsive to the printing of the last dot in the symbol for terminating operation of the local clock pulse generator.

8. An electronic circuit for symbol synthesis wherein a symbol is formed by generating a sequence of visible dots in a matrix of dot locations comprising:

a plurality of control conductors each conductor individual to a dot in the sequence of dots required to define the symbol to be synthesized;

means for applying, in response to generation of each dot in the symbol, a signal to the control conductor individual to said dot being generated;

means responsive to the presence of said signal on said conductor for producing a first and second series of control signals in a two-dimensional, digital representation of the location of the next dot to be generated in the sequence of dots required to define the symbol, and

means for providing said digital representation of the location of the next dot in the sequence to the applying means causing it to apply a signal to the control conductor individual to said next dot.

(References on following page) References Cited UNITED STATES PATENTS Dell 340324.1 Simshauser 340324.1 Fenimore et al. 340--324.1 Larrowe et a1 340324.1 Tolson et a1. 178-30 Gordon et a1. 340--324 22 3,024,454 3/ 1962 Chaimowicz 340-324 3,060,429 /1962 Winston 346 X 3,182,126 5/1962 Ascoli 17830 3,298,030 1/ 1967 Lewis et a1. 34675 JOHN W. CALDWELL, Primary Examiner.

ALAN J. KASPER, Assistant Exwminer.

US. Cl. X.R.

Triest 340424 10 -45; 17830; 340 1725; 34678, 

